Fifty-six crossbred pigs were used in two experiments to evaluate
chopped whole sugar cane stalk as the basal diet. In Experiment 1 the treatments were
different combinations of fish meal, soya bean meal and meat meal with chopped cane at 17%
(fresh basis) of liveweight; in Experiment 2 different offer levels of chopped cane were
compared (17, 14, 10 and 6% of liveweight) with the same protein supplement. Estimates
were made of sugar extraction rate by applying coefficients for ?Brix (total sugars) and
the dry matter content of the stalk residue, after it had been chewed, determined by
Sarria (1996) (Sarria Patricia, personal communication).

In Experiment 1 growth rates from 420 to 580 g/day were obtained on the
chopped cane stalk when soya bean or fish meal were the protein sources; the control pigs
(on maize-soya bean meal) grew at 650 g/day. The extraction rate of sugar by the pigs was
estimated to be 67% resulting in a daily sugar intake of about 1 kg.

In Experiment 2, growth rate decreased linearly as the offer level of
cane stalk was reduced (from 441 to 237 g/day) but sugar extraction rate increased from
67% at the 17% offer level to 84% on the lowest level (6% of liveweight).

Traditionally. small scale farmers in sugar cane growing regions have
fed whole or chopped sugar cane to their pigs. Observations show clearly that the pigs
chew the cane stalk to extract the juice and then "spit-out" most or all of the
fibre; and that they grow slower than on cane juice or cereal grain based diets (Bon-Aimé
et al 1989). However, there is little documented information about the efficiency
with which this feed resource is used by pigs at different stages of the productive cycle;
nor the degree to which the pigs extract the sugars which presumably is influenced by the
offer level.

The following experiments were carried out at CATIE (Centro para la
Agricultura Tropical, Investigación y Ensañanza) in Costa Rica in the early 80s
and are discussed in the light of more recent developments with sugar cane as feed for
pigs (Mena et al 1986; Sarria et al 1990).

Thirty-six crossbred pigs (Large White x Duroc) with an initial weight
of 31 kg and approximately 3.5 months of age were allocated by sex and weight to six
dietary treatments with two replications (pens of 3 pigs). The diets were:

The concentrate used for the control group was a mixture (%) of maize
53, rice bran 34, meat meal 6, soya bean cake 6, salt 0.5 and 0.5 of mineral and vitamin
supplement. On the experimental treatments, the sugar cane stalk was fed chopped in small
pieces using a chopping machine for forages; the chopped pieces were put on the floor
twice a day. The offer level was enough to let the pigs extract the juice and to leave a
residue every day. There was no basis on which to adjust the amount to offer so the method
used was to offer three times the estimated intake for all the treatments. The protein
supplement was fed according to the requirements of NRC (1979). Additionally the pigs
received a mixture of mineral and vitamins.

Data for live weight gain, final weight and feed intake were recorded.
The experiment ended when the pigs on the control treatment reached a mean liveweight of
90 kg.

Experiment 2: Different levels of offer of chopped cane stalk with a
protein supplement for growing-finishing pigs

Twenty crossbred pigs (Duroc x Yorkshire) with an initial weight of 26
kg and approximately 3 months of age were allocated by sex and weight to fourth groups of
three pigs and 4 groups of two pigs. There were four treatments representing offer levels
of cane stalk of 100, 75, 50 and 25% of that used in Experiment 1. There were two
replications (one pen of 3 pigs and one pen of pigs) of each treatment. The diets were:

Chopped sugar cane stalk ad libitum (10 kg/day)(SC100)

Chopped sugar cane stalk restricted at 75% of treatment 1 (SC75)

Chopped sugar cane stalk restricted at 50 % of treatment 1 (SC50)

Chopped sugar cane stalk restricted at 25% of treatment 1 (SC25)

A protein supplement was used based on 50% fish meal and 50% soya meal;
it was fed in amounts calculated to supply the protein requirements recommended by NRC
(1979). The sugar cane stalk was chopped and offered on the floor twice daily. Amounts
offered and refused were recorded. Liveweights were taken at the beginning and end of the
trial.

The experiment was conducted for 142 days.

Results and Discussion

The mean values for liveweights and feed intake are in Tables 1 and 2
for experiments 1 and 2, respectively. The residues are composed of fibre, sugar and
saliva, representing cane stalk which has been chewed and then discarded, after part of
the juice has been extracted. It has been diluted with saliva and is of much lower dry
matter content than the original stalk. Thus simple estimates of intake by subtracting
residues from amounts offered have no meaning. Similarly, estimates of dry matter intake
are also confounded, in this case by the fact that the sugar in the dry matter is
obviously less in the residue than in the material offered. In order to arrive at an
approximation of intake of sugars and conversion rates, calculations were made using data
derived by Sarria (1996, personal communication) from pigs fed similarly with chopped cane
stalk and protein supplement. Sarria measured brix of the juice and the dry matter in both
the cane offered and in the residue. The values were:

Sugar cane stalk: A=30% dry matter and B=20 ºBrix (% total sugars)

Residue: A1=15% dry matter and B1=9 ºBrix

Using these figures the amounts of sugar in the cane offered (cane
offered C=kg/day) can be calculated in the following steps as:

Water in cane = C x (100-A)/100 kg/day

Sugars in cane = [C x (100-A)/100/(100-B) x B] (for every 80 kg of
water there are 20 kg sugars)

It is assumed that the pigs in these experiments extracted the juice
with the same efficiency as those studied by Sarria (1996), that the efficiency would not
be affected by offer level and that the fibre in the sugar cane stalk did not contribute
any nutrients. These assumptions are unlikely to hold in exact terms, however, they
provide an oportunity to get some idea of the approximate amounts of sugars consumed and
the overall feed conversion.

The observations in Experiment 1 show that reasonable growth rates can
be obtained (450-500 g/day compared with 650 g/day on the cereal-based control) when sugar
cane stalk is fed at the rate of 17kg (fresh basis) for every 100 kg liveweight and the
protein supplement is provided by fish meal, soya bean or a mixture of the two. Results
with meat meal were much poorer. It was estimated that actual intakes of sugars were of
the order of 1 kg/day giving feed conversion ratios (DM basis) slightly poorer than on the
control diet.

The average amount of cane fed (9.5 kg/day) would have yielded slightly
less than 5 litres of juice if it had been passed through a 3-roll mill. This would not
have been enough to support the recorded liveweight gains of 450-550 g/day on the basis of
the recommendations of Sarria et al (1991). This implies that the pigs were
extracting more juice by chewing than a 3-roll mill.

Thus the efficiency of the pig in extracting the sugars appears to be
higher than that of a typical 3-roll mill used for artisan sugar production. Extraction
rates in such mills are of the order of 50% (50 kg juice from 100 kg cane stalk) which is
equivalent to about 56% of the total sugar in the cane. From the data in tables 1 and 2,
it can be calculated that the pigs extracted about 67% in Experiment 1 when offer rate was
high (17% of liveweight) while an extraction rate of 84% was reached in Experiment 2 when
the amount offered was restricted to 10% of liveweight.

Lower offer level of cane and, as a result, higher extraction rate of
sugars, reduces cost of inputs (the sugar cane) but causes a reduction in gross return
(rate of liveweight gain). Research is needed to establish the relationship between these
contrasting criteria for different stages of the growth and reproductive cycles of the
pigs.

Conclusions

Pigs grew satisfactorily (450-550 g/day) when given free access to
fresh chopped sugar cane stalk (17% of liveweight) supplemented with soya bean meal or
fish meal. Extraction rate of sugars was about 67% which is higher than what is achieved
with a 3-roll mill used for artisan juice extraction.

As offer level was reduced, rate of gain in liveweight decreased
linearly but extraction rate appeared to increase, reaching 84% at the 6% of liveweight
offer level.